Lighting systems typically rely on conventional lighting technologies, such as incandescent bulbs and fluorescent bulbs. But these lighting technologies suffer from several drawings. For example, such light sources do not offer long life or high energy efficiency. Consequently, light-emitting diodes (LEDs) have become an attractive option for many applications.
A “light engine” is the LED equivalent of a conventional light source. Light engines include at least one LED that is mounted on a rigid/flexible board (also referred to as an “LED module”) and an LED driver (also referred to as “electronic control gear”). Light engines are widely used in various applications, such as indicators, signs, light crystal display (LCD) backlights, automobile headlines, medical devices, and optical communications. For example, the LED module(s) may be disposed on a printed circuit board having electrical fixings and mechanical fixings that allow the printed circuit board to be readily fixed in a luminaire.
One challenge for LED technology is using conventional dimming control mechanisms (also referred to as “lighting control mechanisms”) to control the light output level of an LED. One example of a conventional lighting control mechanism is a dimmer control that operates in accordance with an analog 0-10V lighting control protocol. In such instances, the control signal for the LED is a direct current (DC) voltage that varies between zero and ten volts to produce a varying intensity level. At intermediate voltages between 0V and 10V, the output curves of the LED can have various patterns. For example, an output curve could be linear for voltage output, actual light output, power output, or perceived light output. Typical 0-10V wiring diagrams are shown in FIG. 1A-B.
There are two existing 0-10V dimming standards: current source (“source”) type and current sink (“sink”) type. Because these dimming standards are not compatible with one another, it has historically been essential for a control system to understand which type is required for a given application.
The source type was originally developed for theatrical lighting applications. A source type dimmer control provides a separate 0-10V control voltage to each dimming channel that is connected to a luminaire. Thus, the source type dimmer control directly feeds the control voltage(s) to the LED(s). For the source type, 10V is defined as 100% of the designed potential output while 0V is defined as off (i.e., 0% light output).
The sink type was originally developed for controlling fluorescent dimming ballasts. A driver or a fixture control card generates a power signal that is delivered to a sink type dimmer control. The sink type dimmer control modulates the power signal between zero and ten volts by “sinking” its power with the driver, which in turn changes the control voltage. In other words, a power supply sinks the current and the sink type dimmer control provides the voltage for the LED(s). For the sink type, 10V (or above) is defined as 100% of the designed potential output. As the control voltage is reduced by the sink type dimmer control, the light output is reduced accordingly. However, the minimum control voltage defines and sets the minimum light output level. Thus, the minimum light output level depends on the driver. Some drivers' minimum light output level is off (i.e., 0% light output) while other drivers' minimum light output level is the lowest light level of the driver.
The figures depict various embodiments for the purpose of illustration only. One skilled in the art will recognize that alternative embodiments may be employed without departing from the principles of the technology described herein.